1. Field of the Invention
The present invention relates to a pipe liner bag which is mainly used for repairing pipelines, and manufacturing methods therefor.
2. Description of the Related Art
When an underground pipe, such as pipelines and passageways, becomes defective or too old to perform properly, the pipe is repaired and rehabilitated without digging the earth to expose the pipe and disassembling the sections of the pipe. This non-digging method of repairing an underground pipe has been known and practiced commonly in the field of civil engineering. The pipe lining method utilizes a tubular pipe liner bag made of a resin absorbent material impregnated with a hardenable resin, and having the outer surface covered with a highly air-tight plastic film. The tubular pipe liner bag is inserted into a pipe to be repaired by means of a pressurized fluid such that the pipe liner bag is turned inside out as it proceeds deeper in the pipe. Hereinafter, this manner of insertion shall be called "everting". When the entire length of the tubular liner bag is everted (i.e., turned inside out) into the pipe, the everted tubular liner is pressed against the inner wall of the pipe by a pressurized fluid, and the tubular flexible liner is hardened as the hardenable resin impregnated in the liner is heated, which is effected by heating the fluid filling the tubular liner bag. It is thus possible to line the inner wall of the defective or old pipe with a rigid liner without digging the ground and disassembling the pipe sections.
Meantime, tubular resin absorbent materials generally and widely used for the pipe liner bag in the pipe lining method mentioned above include unwoven fabrics such as polyester, acrylic resin, polypropylene, or the like (for example, refer to Japanese Provisional Patent Publication (Kokai) No.4-59227). The processing methods of the unwoven fabric are roughly classified into two: a needle punching method and a spun bond processing method.
Conventionally, any unwoven fabric may be used as it is so long as the unwoven fabric, after being subjected to the processing, has the characteristics suitable for the pipe liner bag, irrespective of the method it is processed.
Meantime, of the pipe liner bag of the type which is everted and inserted into the pipeline by fluid pressure, the outer surface (this comes out to be the inner surface after being everted) of the tubularly processed unwoven fabric needs to be coated by a highly air-tight plastic film, and the plastic film has two types: one that remains as it is on the inner peripheral surface of the unwoven fabric, after the lining process, to constitute the inner surface of the pipe liner bag, and the other that is peeled from the inner surface of the unwoven fabric after the lining process.
Of the pipe liner bag of the type where the plastic film coated on the inner circumferential surface of the unwoven fabric remains as it is after the lining process, the plastic film must have a high anti-peeling strength. The reasons for the requirement of high anti-peeling strength are as follows. First, the plastic film needs to have high anti-peeling property since the plastic film is, after the lining process, subjected to the friction of the fluid that flows in the pipeline and to the injection pressure of the high pressure water used for cleaning the pipeline. Second, the plastic film needs to have high anti-bursting properties since the plastic film is subjected to the fluid pressure during the lining operation.
Further, with regard to the anti-bursting property, when the plastic film is evenly and firmly adhered or, on the contrary, not adhered at all to the unwoven fabric, the plastic film has high anti-bursting property, and when the anti-peeling strength is weak due to the plastic film being unevenly adhered to the unwoven fabric, the plastic film unevenly extends, thus causing a deteriorated anti-bursting property.
In such a circumstance, as means to increase the anti-peeling strength of the plastic film against the unwoven fabric, such methods are conceivable that the plastic film is made thicker to give more welding deposits to the unwoven fabric so that the adhering property of the plastic film against the unwoven fabric may be increased and that the thermo-adhesive film having stronger property to adhere to the thread of the unwoven fabric is used as the plastic film.
However, even if the adhering quality of the plastic film against the unwoven fabric is increased, it is impossible for the unthreadable unwoven fabric to ensure high anti-peeling strength on the plastic film.